In the past, a vast number of solutions have been proposed for converting a wheeled vehicle into a tracked vehicle. According to one of these solutions a monolithic flexible track is installed around a pair of wheels remote from each other on the same side of a vehicle, at least one of the wheels being a driven wheel. To prevent elongation of the track during use, the track is reinforced in longitudinal direction, for example by one or more steel or textile fibers or cords.
GB-A-2.104.015 discloses a flexible endless track, which is made of an elastomeric material reinforced with nylon or steel filamentary material in the form of a continuous cord wound across the width of the track in a plurality of side-by-side turns. As this track is endless, continuous, the tires of the wheels need to be deflated when mounting or the track around them or removing the track. This operation is complicated and time consuming.
Another solution for adapting a wheeled truck having the wheels arranged in two adjacent sets to agricultural purposes and to make it suitable for traveling with heavy loads on weak soil has been proposed by U.S. Pat. No. 4,362,340. According to U.S. Pat. No. 4,362,340 an endless tread type track is mounted around a pair of consecutive tires. The track is made of a flexible material, for example a synthetic resin or rubber-like material and contains one or more canvas or nylon liners. The track may either be built up of a single part both ends of which are interconnected when mounted to a vehicle to form an endless belt, or of two or more parts, which are connected to each other by two or more joints. On the side of the belt facing the tires, a plurality of cams or teeth having the shape of a truncated pyramid is present. The cams or teeth are held in a clamping fit between two adjacent tires.
An analysis of the problems arising with the above-described type of tracks has revealed that they are driven by a circumferential traction exerted by the wheels to the track. To provide good transfer of the traction forces, the track needs to be tensioned around the wheels. However, tension has been found to decrease during use of the track. Besides this, the traction provided by the cams positioned between the adjacent tires appears to be insufficient, slipping at the front side of the vehicle being the result.
In DE-U-9302375.8 a flexible belt for use as a track is disclosed, which solves the problem of minimizing the risk to elongation following use, as this adversely affects the contact between the track and it's driving. The flexible belt disclosed in DE-U-9302375.8 is provided to be used as such; there is no teaching to use this belt in combination with a wheeled vehicle. The belt disclosed in DE-U-9302375.8 comprises a plurality of parallel bands connected to each other in cross direction of the track, each band being internally reinforced by a plurality of metal cords. The coupling of parallel bands in cross direction of the truck is achieved by means of a plurality of U-shaped profiles, each U-profile being received in corresponding recesses in the parallel bands. Each band has an opposite first and second end part. Each end part contains a central coupling hole for coupling the first end part to the second end part in longitudinal direction of the track, a reinforcing cord extending as a loop around the coupling hole.
U.S. Pat. No. 3,161,443 discloses a positive drive tractor track adapted to be stretched about the outside surface of consecutive tractor wheels, one of them having a larger size, one of them having and a smaller size. Soil engagement of the outer surface of the track is improved by the presence of transversally extending ribs reinforced with rods. The rods are connected to each other in longitudinal direction by means of longitudinally extending steel wires, which also function as track absorbing members. The track is driven and held firmly on both wheels by means of projections along the longitudinal track edges, which are provided to engage between the ribs sideways of the tires. The projections extend in steps of different height to render them suitable for use with wheels of different size. Both end parts of the track are joined by means of joining lugs. However, the ability of the track to deform in longitudinal direction and to adapt itself to varying dimensions of the wheels is limited, thus leading to poor circumferential traction. Besides this, the track shows a serious risk to slipping at large powers in which case there is no engagement of the protrusions and no driving of the track. Also the track is subject to vibrations as the inwardly projections engage between the ribs. The track disclosed in U.S. Pat. No. 3,161,443 is not suitable for use with small wheels as in that case the number of contact points between the track and wheels is insufficient.
U.S. Pat. No. 2,560,307 discloses an endless track assembly extending about spaced-apart pulleys, which solves the problem of improving mud removal from the space between the pulley and the track. Thereto the inner surface of the track is provided with a pair of circumferentially extending longitudinal ribs with a continuous valley-like depression between them engageable with circumferential rims on opposite sides of the pulley. The resilient rubber material at the pulley-contacting surface of the track accommodates variations in the surfaces of the rim, to improve the grip on the pulley for effective driving action. Transmission of traction force with minimum slippage between the track and the soil is obtained by the presence of corrugations on the ground-contacting surface of the track. The sliding and contacting movement of the ribs across the inclined portions of the corresponding rim on the pulley scrapes the exposed working surfaces substantially free of mud. The pressing action of the bottom wall of the valley like depression tends to squeeze the mud from between the adjacent faces of the band and the pulley and to shift the mud to the peripheral groove which accommodates the mud and permits it to travel with the pulley to an upper region of the pulley, thereby facilitating frictional engagement between the peripheral contacting surfaces of the band and pulley at each side of the groove for effective traction purposes.